1. Field of the Invention
The present invention relates to metal fittings for connecting between a transformer side and a welding gun side used for a resistance welder.
2. Description of the Prior Art
For connecting a welding gun to a transformer side, it is usually required not only to connect their terminals to each other but also to connect a cooling water line to an air supply line.
For example, Japanese Utility Model Laid-Open Publication No. 59-120083 discloses prior connecting metal fittings employing receiver metal fittings and clamping metal fittings. This type of connecting metal fittings will be described below with reference to FIGS. 5, 6.
Designated at 1 is receiver metal fittings including a pair of power supply connecting strips 4, 4 connected to terminal plates 3, 3 on the transformer side, a pair of first cooling water lines 5, 5 connected to a supply side water supply circulating line and a pair of first air supply lines connected to a supply side air supply circulating line. A rotatable first clamping handle 20 having a recessed part 19 for fitting provided in a handle shaft lever is mounted on the receiver metal fittings 1. Clamping metal fittings 2 include a clamping screw lever 21 penetrating terminal strips 10, 10 on the welding gun side and respective notched grooves 31 of the power supply connecting plates for clamping the plates on the terminal strips, a pair of first air supply lines 17, 17 connected to a welding gun side water supply circulating line, a pair of second air supply lines 18, 18 connected to a welding gun side air supply circulating line, and a pair of fitting projection pieces 22, 22 fitting in the fitting recessed parts 19, 19. A second clamping handle 23 mounted on the clamping screw lever 21 is provided on the clamping metal fittings 2. The clamping screw lever 21 includes opposing right and left screws 24a, 24b formed therein as well as the fitting projection pieces 22, 22 include opposing right and left screws 25a, 25b having the opposing screws 24a, 24b threaded therein.
For connecting the welding gun side with the transformer side, the receiver metal fittings 1 and the clamping metal fittings 2 are brought into close vicinity to each other, and with the first clamping handle 20 rotated, the engagement recessed parts 19, 19 are forced to engage with the engagement projection pieces 22, 22, and thereby both the metal fittings 1, 2 are closely connected with each other. In succession, with the second clamping handle 23 rotated the terminal plates 10, 10 are clamped by means of the power supply connecting strips 4, 4 to accomplish the connection therebetween.
Both the metal fittings 1, 2 may be detached by operating the respective clamping handles in reverse.
However, such prior clamping metal fittings suffer from some drawbacks: First and second two handles must be operated as a clamping handle for connecting both the metal fittings with each other. Namely, after operation of the first handle, the second one must be operated in succession, thus resulting in troublesome operation. In addition, there may be a case where only the first handle is operated and operation of the second one is forgotten. In such a case, since the terminal plate 10 and the power supply connecting strip 4 are not closely clamped, operation of a welder not only causes insufficient current to be supplied to a welding gun, but also produces a considerable amount of heat therebetween, thereby causing the possibility of damaging the connecting metal fittings.